We went to Outback Steakhouse tonight and I had a steak. My youngest child had a sandwich.
(This is not the sandwich).
She was only able to eat half of the sandwich. My general rule is that if you take a bite out of something, you should not take it with you. It is only safe if you cut off portions with your knife.
If you take bites out of it, the bacteria will grow on it and you will be eating bacteria later.
Would you box up a half eaten sandwich?